When the user explicitly clicks the SEARCH icon, 
the app LPG/CNG price reporter sends the 
* GPS posision of the phone and 
* an identifier for this app that is the same on all phones of all people
* the type of fuel to the API of gas-tankstellen.de 
to 
* request current prices and details of nearby GPL and CNG fuel stations.

If the user has added credentials for gas-tankstellen.de
and the user either 
clicks the icon that the shown price is still OK or
clicks the icon that the price is no longer accurate and enters a price
the app LPG/CNG price reporter
* transmits the credentials
* and the entered price
* and the identification of that fuel station
to gas-tankstellen.de using the provided user credentials
to
* update the price information.

Android Permissions:

The Android permission .READ_PHONE_STATE is NOT USED. It simply didn't exist back when this app was written and is thus automatically required by all apps.
It still works fine every day.
Adapting it to a modern SDK serves no practical purpose and is a lot of work because all the maps APIs used have changed and require a full rewrite.